Refrigerating apparatus, incluiding defrosting means



Jan. 4, 1955 L. J. MANN 2,698,521

REFRIGERATING APPARATUS, INCLUDING DEFROSTING MEANS Filed Jan. 4, 1952United States Patent '0 REFRIGERATING APPARATUS, INCLUDING DEFROSTINGMEANS Leonard 3. Mann, Dayton, Ohio, 'assigrior to General MotorsCorporation, Dayton, Ohio, a corporation of Deiaware Application January4, 1952, Sei'ial No. 254,935

4-Claims. =(CL' 62 4) This invention relates to refrigerating apparatusand more particularly to a system for defrosting evaporate-rs.

Various systems have 'been devised for defrosting evaporatorsautomatically but there has alwaysbeenditfi culty in causingthis'defrosting to take place uniformly. Particularly it has beenfoundthat, adjacent the inlet and outlet connections of certain'evaporators and the connections themselves, there has been difficultyin removing the frost from these portions and keeping the frost removed.If the'defrosting cycle were lengthened, then refrigerator would'becometoo warm before all portions were completely defrosted.

It is an object of my'invention'to provide'an additional supply of heatadjacent 'the portion which is most dinicult to defrost.

It is another object of my invention to seal-range the refrigerator thatthe heat absorption by the evaporator is greatest adjacent therefrigerant'supply and return con nections.

It is another-object of my invention to apply the condenser of asecondary refrigerant circuit to that portion of the evaporator and alsoto the adjacent portions of ;he refrigerant conduit where it isditficult 'to remove the rost.

It is another object of my invention to provide an upright rectangulartype of evaporator having the refrigerant connections adjacent the uppercorner with a vertical condenser tube of which the lower portion is inheat exchange relation with that corner'of 'the plate and the upperportion of which is inh'eat exchange relation with the conduits.

It is another object of my invention 'to applyto a refrigerator having aseparate insulated freezing 'cor'npartment and a food compartmentprovided with an upright rectangular refrigerant plate, asecondaryrefrigerant circuit for cooling portions of the food compartment whichhas a vertical condenser located adjacent an upper corner of therefrigerated plate where the refrigerantsupply and return conduits to itare located.

These Objects are obtained by providing in the food cornpartment avertical refrigerant plate having supply and return connections at anupper corner extending from the primary or freezing evaporator. Asecondary refrigerant circuit having its evaporator located beneath thebottom of the food compartment 'has avertie'al tunnlar condenser withits lower portion in direct Contact with the end portion of therefrigerated plate and its extreme upper portion clamped in heatexchange relation with the supply and return conduits. The "systemoperates upon a defrosting cycle according "to the temperature of thediagonally opposite, corner of the refrigerated plate. By thisarrangement, the freezing evaporator is kept at all times at a'lowtemperature "and'the refrigerated plate in the food compartment providesproper temperature and humidity conditions and defrosting both of theplate and the supply connections is obtained every cycle.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawing, wherein a preferred form of the present invention is clearlyshown.

In the drawing:

The figure is a vertical sectional view of a two-compartmentrefrigerator embodying one form of my invention.

Referring now to the drawing, there is provided an outer hermeticallysealed sheet metal shell 20 enclosing the cabinet. The joints of thisshell are sealed. There is of the cabinet in the form of abox-'shapedfmetal ed11- tainer having its front side open. Beneath thefreezing compartment container 32 there is'provided a'foodco'rnpartmentcontainer 38 in the form of 'a'box-shapedini'et'al inner'containerorliner, also having its front side open. The front edges of thebox-shaped container 32 and 38 are connected by breaker strips of heatinsulating rn'ate'rial "with the frontwall'of the outer shell 20 as isoil'stomary in the art. The freezing compartment container 32 and thefood compartment'container 38 are preferably closed by separate frontdoors (-not shown). The spaces between these containers 32 and 38 andthe walls of the outer shell are filled with insulation such as"thineralor glass wool enclosed'in sealed bags of somesuitahle materialsuch as polyethylene.

The freezing compartment container 32 is provided with smooth surfacedinner walls so that any snow or frost accumulating thereon can bereadily scraped or brushed off. The freezing compartment container 32 iscooled by the evaporating stage of a prnn'ary refrigcrating system whichincludes a sealed motor compressor unit which delivers compressedrefrigerant to a condenser 52, both of which are located inamachinejcoinpartment 161 beneath the partition wall 24 of the cabinet20. The motor compressor unit50 is 'preferably'o'f tlie high side typeshown in the Rataiczak Patent 2,377,965, issued June 12, 1945.

The condenser 52 delivers liquid refrigerant through a capillary tuberestrictor '54 to the inlet connection of serpentine tubing 57 appliedto the rear wallof the container'SZ'and loops 58, 59 and 60 appliedto'the teens-y shelves at one side of the;container 32. From the loop 60the refrigerant passes into sections 61 of'evapo'ra'tor tubing whichextend in heat'exchange relation with the top, bottom and sides ofthecontainer 32.

7 After passing through a liquid trap at the endof the tubing 61, therefrigerant is conducted through a supply conduit 72-to a verticalrectangular refrigerated plate type evaporator Q0 spaced from, butfastened to, the rear wall of the food compartment container 38 withinand near the top of the food compartment. The refrigerated plate 90 hasa minimum of mass and low hold-over capacity. It is provided with 'arefrigerant passage 91 which extends'along the "edges of therefrigerated plate evaporator 99 having its inlet '89 connected to thesupply conduit "2 and its outlet 87 connected to the return conduit 94adjacent the upper left-hand corner of the plate 90 as shown in thefigure. The return conduit 34 connects to an accumulator tank 96 locatedalong the upper rear edge of the freezing compartment container 32. Thesuction conduit 125 extends from this accumulator tank 96 to the suctioninlet of the compressor 58.

The operation of the motor-compressor unit 50 is controlled by asnap-acting thermostat switch 89 connected in series with the supplyconductor 81 of the motorcompressor unit 50. This switch is set tooperate upon a defrosting cycle and has its thermo-sensitive element 378clamped to the lower right-hand corner of the refrigerated plate 9i? insubstantially direct heat exchange relation with the refrigerant passage95. The thermosensitvie element 370 is located upon the plate withrespect to the refrigerant passage 91 at such a location which willprovide a control of the amount'of liquid rejfrigerant in the passage 91during the operating period thesy'stem to provide the desired averagetemperature for the interior of the food compartment 81. The switch '84is set so that it will not close until the rtempera'tur'e of thethermo-sensitive element reaches a defrosting tern; perature such as 34to 36 degrees Fahrenheit. The switch '30 is set to open at as'utficiently low temperature below freezing, such as 0 to 10 degreesFahrenheit, which will assure adequate cooling for the food compartment38.

The freezing compartment container 32 is sufficiently isolated thermallyfrom the food compartment 38 and the refrigerated plate 90 and therefrigerated plate 90, in general, defrosts sufiiciently rapid that thefood compartment container 32 and its contents remain at a lowsub-freezing temperature at all times. However, ditliculty wasencountered in defrosting the upper corner of the refrigerated plate 90adjacent the inlet and outlet 89 and 87 and the adjacent portions of therefrigerant sup ply and return connections 72 and 94. On these surfacesfrost would not melt completely during the idle period of therefrigerating system and, consequently the frost and ice would build upand accumulate until a large mass was obtained. This made it necessaryto shut down the entire refrigerating system and to remove and store, inanother cold place, the contents of the freezing compartment container32.

At the bottom of the food compartment container 38 there are providedtwo ventilated vegetable drawers 127 and 129 which provide a moist coldatmosphere/ To keep these drawers 127 and 129 at a sufiiciently lowtemperature, there is provided a secondary refrigerant circuit includingan evaporating portion 131 in the insulation space immediately beneaththe bottom of the food compartment container 38. The condenser of thesecondary circuit has been located in various points in otherrefrigerators. For example, the condenser has been located in heatexchange relation with the freezing container 32. It has been placed onthe rear wall of the food compartment container 38 adjacent the plate90. It has also been placed in heat exchange relation with the centralportion of the plate 90. These locations were not ideal.

To provide satisfactory operation of the system and complete defrostingof all refrigerated surfaces in the food compartment 38 every cycle, Iprovide a long vertical tubular condenser 137. The upper third of thiscondenser 137 I clamp by means of the clamp 138 to the supply and returnconnections 72 and 94 nearest the inlet and outlet 89 and 87 on the backside of the plate 90. The lower two-thirds of the condenser 137 is alsoclamped in direct heat exchange relation with the upper left-hand cornerof the refrigerated plate evaporator 90 in vertical position directlybetween the inlet 89 and the outlet 87 as shown in the drawing. Thiscondenser 137 is connected by supply and return conduits 133 and 135with the secondary evaporator 131 as shown in the drawing. Accordingly,the secondary refrigerant circuit provides an added source of heat forthe upper left-hand corner of the refrigerated plate 90 and the adjacentportions of the supply and return conduits 72 and 94 which in priorarrangements defrosted more slowly than the remainder of the plate 90,thereby hastening the defrosting of this portion of the refrigeratedplate 90 during each cycle period of the compressor. In this way,adequate refrigeration is provided for the secondary circuit and at thesame time defrosting of all refrigerated surfaces in the foodcompartment 38 is assured every cycle, thereby overcoming the previouslyencountered difficulty of the accumulation of frost upon this portion ofthe refrigera1te9d4plate 90 and the supply and return connections 72 anWhile the form of embodiment of the invention as herein disclosedconstitutes a preferred form, it is to be understood that other formsmight be adopted as will come within the scope of the claims whichfollow.

What is claimed is as follows:

1. Refrigerating apparatus including an above f eezing food compartmentand a below freezing compartment, a thermal heat transfer barrierbetween said compartments, a refrigerant liquefying means, a freezingevaporating means in heat exchange relation with said below freezingcompartment and having its inlet connected to an outlet of saidliquefying means, a food compartment evaporating means in heat exchangerelation with said food compartment and having its inlet connected to anoutlet of said freezing evaporating means, means for returningevaporated refrigerant from said freezing and food compartmentevaporating means to said liquefying means, a secondary refrigerantcircuit having an evaporating portion in heat exchange relation with aportion of said food compartment and a condensing portion in heatexchange relation with the portion of the food compartment evaporatingmeans nearest the refrigerant inlet and means responsive to thetemperature of the food compartment evaporating means for cyclicallycontrolling the supply of refrigerant to said an outlet of saidliquefying means, a food compartment,

evaporating means in heat exchange relation with said food compartmentand having its inlet connected to an outlet of said freezing evaporatingmeans, means for returning evaporated refrigerant from said freezing andfood compartment evaporating means to said liquefying means, a secondaryrefrigerant circuit having an evaporating portion in heat exchangerelation with the lower portion of said food compartment and an uprightcondensing portion having a portion in heat exchange with therefrigerant inlet connection to said food compartment evaporating meansand a portion in heat exchange relation with an adjacent portion of thefood compartment evaporating means and means responsive to thetemperature of the food compartment evaporating means for cyclicallycontrolling the supply of refrigerant to said food compartmentevaporating means so as to vary the temperature thereof below and abovefreezing during each cycle so as to defrost said food compartmentevaporating means once each cycle.

3. Refrigerating apparatus including an insulated refrigerator cabinetcontaining a first low temperature compartment and a second highertemperature compartment, a first evaporator in said first compartment,an upright plate type refrigerant evaporator located in direct heatexchange relation with air in said second compartment, refrigerantsupply and return conduits connected to said plate type evaporator,refrigerant liquefying means connected to supply liquid refrigerant tosaid evaporators in series, a secondary refrigerant circuit including anevaporating means in heat exchange relation with a portion of saidcompartment and a condensing means in heat exchange relation with theportion of said plate evaporator nearest the refrigerant supply conduit,and means responsive to the temperature of said plate evaporator forcyclically controlling the supply of refrigerant to said plate typeevaporator so as to vary the temperature thereof below and abovefreezing during each cycle so as to defrost said plate evaporator onceeach cycle.

4. Refrigerating apparatus including an insulated cabinet having a foodstorage compartment therein, an upright plate type rectangularrefrigerant evaporator adjacent to but spaced from the rear wall of saidcompartment and having a refrigerant passage extending along the edgesthereof with the inlet and outlet located adjacent an upper cornerthereof, supply and suction conducits connecting to said inlet and'outlet, refrigerant liquefying means connecting to said conduits, asecondary refrigerant circuit including a condensing means in heatexchange relationtwith the upper corner of said plate evaporator adacent said inlet and outlet, and in heat exchange relation with theportion of said conduits ad- References Cited in the file of this patentUNITED STATES PATENTS 2,282,342 Preble May 12, 1942 2,301,313 Money-Nov. 10, 19-42 2,484,588 Richard Oct. 11, 1949 2,491,105. Gaugler Dec.13, 1949 2,561,305 Limpert July 17, 1951

